There might have been some input lag before the PC patch, but I don't think I've had any problems since then. Even then, the only thing I can specifically remember that might have been input lag was during the Hurdle Hijinx game, and I'm pretty sure that was a glitch rather than input lag.

Sorry for the double post, but I did just remember a place where I definitely had input lag: the final boss, during the outside part of the battle. It was so bad that I decided to stop trying on the 3-butterfly mode. This happened - notably - after the patch was applied. I think I remember slight lag in that battle before the patch, but I definitely know there is lag afterwards. At least for me there is.